In function `tc_dump_tfilter`, the attributes array is parsed via
tcf_tfilter_dump_policy which only describes TCA_DUMP_FLAGS. However,
the NLA TCA_CHAIN is also accessed with `nla_get_u32`.

The access to TCA_CHAIN is introduced in commit 5bc1701881e3 ("net:
sched: introduce multichain support for filters") and no nla_policy is
provided for parsing at that point. Later on, tcf_tfilter_dump_policy is
introduced in commit f8ab1807a9c9 ("net: sched: introduce terse dump
flag") while still ignoring the fact that TCA_CHAIN needs a check. This
patch does that by complementing the policy to allow the access
discussed here can be safe as other cases just choose rtm_tca_policy as
the parsing policy.

Signed-off-by: Lin Ma <linma@zju.edu.cn>
---
V1 -> V2: send to net-next as told by Jamal <jhs@mojatatu.com>

 net/sched/cls_api.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
index 1976bd163986..2b5b8eca2ee3 100644
--- a/net/sched/cls_api.c
+++ b/net/sched/cls_api.c
@@ -2732,6 +2732,7 @@ static bool tcf_chain_dump(struct tcf_chain *chain, struct Qdisc *q, u32 parent,
 }
 
 static const struct nla_policy tcf_tfilter_dump_policy[TCA_MAX + 1] = {
+	[TCA_CHAIN]      = { .type = NLA_U32 },
 	[TCA_DUMP_FLAGS] = NLA_POLICY_BITFIELD32(TCA_DUMP_FLAGS_TERSE),
 };
 
-- 
2.17.1

On Thu, Dec 28, 2023 at 02:43:58PM +0800, Lin Ma wrote:
> In function `tc_dump_tfilter`, the attributes array is parsed via
> tcf_tfilter_dump_policy which only describes TCA_DUMP_FLAGS. However,
> the NLA TCA_CHAIN is also accessed with `nla_get_u32`.
> 
> The access to TCA_CHAIN is introduced in commit 5bc1701881e3 ("net:
> sched: introduce multichain support for filters") and no nla_policy is
> provided for parsing at that point. Later on, tcf_tfilter_dump_policy is
> introduced in commit f8ab1807a9c9 ("net: sched: introduce terse dump
> flag") while still ignoring the fact that TCA_CHAIN needs a check. This
> patch does that by complementing the policy to allow the access
> discussed here can be safe as other cases just choose rtm_tca_policy as
> the parsing policy.
> 

This patch looks good but you could use NLA_POLICY_MAX() to validate
TCA_CHAIN while you are on it.

Thanks.

On Thu, Dec 28, 2023 at 1:44 AM Lin Ma <linma@zju.edu.cn> wrote:
>
> In function `tc_dump_tfilter`, the attributes array is parsed via
> tcf_tfilter_dump_policy which only describes TCA_DUMP_FLAGS. However,
> the NLA TCA_CHAIN is also accessed with `nla_get_u32`.
>
> The access to TCA_CHAIN is introduced in commit 5bc1701881e3 ("net:
> sched: introduce multichain support for filters") and no nla_policy is
> provided for parsing at that point. Later on, tcf_tfilter_dump_policy is
> introduced in commit f8ab1807a9c9 ("net: sched: introduce terse dump
> flag") while still ignoring the fact that TCA_CHAIN needs a check. This
> patch does that by complementing the policy to allow the access
> discussed here can be safe as other cases just choose rtm_tca_policy as
> the parsing policy.
>
> Signed-off-by: Lin Ma <linma@zju.edu.cn>

Acked-by: Jamal Hadi Salim <jhs@mojatatu.com>

cheers,
jamal

> ---
> V1 -> V2: send to net-next as told by Jamal <jhs@mojatatu.com>
>
>  net/sched/cls_api.c | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/net/sched/cls_api.c b/net/sched/cls_api.c
> index 1976bd163986..2b5b8eca2ee3 100644
> --- a/net/sched/cls_api.c
> +++ b/net/sched/cls_api.c
> @@ -2732,6 +2732,7 @@ static bool tcf_chain_dump(struct tcf_chain *chain, struct Qdisc *q, u32 parent,
>  }
>
>  static const struct nla_policy tcf_tfilter_dump_policy[TCA_MAX + 1] = {
> +       [TCA_CHAIN]      = { .type = NLA_U32 },
>         [TCA_DUMP_FLAGS] = NLA_POLICY_BITFIELD32(TCA_DUMP_FLAGS_TERSE),
>  };
>
> --
> 2.17.1
>